Underwater drilling methods and apparatus

ABSTRACT

Broadly, three embodiments are disclosed: a first involving drilling a well from a submersible vessel, a second specifically adapted to drilling a well in shallow water, and a third specifically adapted to drilling a well in deep water. In the second and third embodiments, drilling may be accomplished by workmen on the surface of the water. In each embodiment, an anchor pad is first installed at the selected site of the wellhead. Means is disclosed for performing the cementing of the anchor pad underwater. Drilling is effected through a hollow, watertight capsule, which is secured directly or indirectly to the anchor pad, and casing is lowered into the well. In the second and third embodiments, casing extension is mounted on the wellhead within the capsule and run to the surface of the water. After completion of the drilling operation, the casing extension, if used, is removed, a christmas tree is installed in the capsule, and the capsule is sealed to protect the wellhead during the production cycle. A service chamber facilitates return of workmen periodically to the capsule for inspection and repair. Chambers and adaptors facilitating underwater separation of oil and gas and storage of the oil are provided, and a floating production buoy facilitating support of wellhead equipment and product collection by a tanker is also provided. Hydraulic apparatus with suitable electrical actuating means is disclosed for facilitating remote control of a number of operations including positive hold-down of one chamber mounted underwater atop another, sealing of one chamber to another, raising and lowering of the christmas tree within the capsule, and the coupling together of product-bearing lines in one chamber to product-bearing lines in an adjacent chamber.

United States Patent Blanding et al.

451 May9,1972

[54] UNDERWATER DRILLING METHODS AND APPARATUS [72] Inventors: John E. Blanding, Old Lyme, Conn.; Ed-

mund C. Trageser, Webster, N.Y.; James Vincent Harrington, Groton, Conn.

[73] Assignee: General Dynamics Corporation, New

York, NY.

[22] Filed: Mar. 23, 1970 [21] Appl. No.: 21,976

Related US. Application Data [60] Division of Ser. No. 671,532, Sept. 11, 1967, Pat. No. 3,503,443, which is a division of Ser. No. 193,040, Apr. 26, 1962, Pat. No. 3,353,364, which is a continuation-in-part of Ser. No. 81,543, Jan. 9, 1961,

abandoned.

[52] U.S.Cl ..166/.5, 175/6 [58] Field of Search ..166/.5, .6; 175/6; 61/69; 340/2, 3

[56] References Cited UNITED STATES PATENTS 2,783,970 3/1957 Gillespie ..166/.5 X

2,520,520 8/1950 Woodward... .....340/2 X 3,063,507 11/1962 ONeill et al ..166/.5 X

FOREIGN PATENTS OR APPLICATIONS 160,865 4/1921 Great Britain ..l66/.5

Primary Examiner-Ernest R. Purser A!!0rney-Brumbaugh, Graves, Donohue & Raymond [57] ABSTRACT Broadly, three embodiments are disclosed: a first involving drilling a well from a submersible vessel, a second specifically adapted to drilling a well in shallow water, and a third specifically adapted to drilling a well in deep water. In the second and third embodiments, drilling may be accomplished by workmen on the surface of the water.

In each embodiment, an anchor pad is first installed at the selected site of the wellhead. Means is disclosed for performing the cementing of the anchor pad underwater. Drilling is effected through a hollow, watertight capsule, which is secured directly or indirectly to the anchor pad, and casing is lowered into the well. In the second and third embodiments, casing extension is mounted on the wellhead within the capsule and run to the surface of the water.

After completion of the drilling operation, the casing extension, if used, is removed, a christmas tree is installed in the capsule, and the capsule is sealed to protect the wellhead during the production cycle.

A service chamber facilitates return of workmen periodically to the capsule for inspection and repair. Chambers and adaptors facilitating underwater separation of oil and gas and storage of the oil are provided, and a floating production buoy facilitating support of wellhead equipment and product collection by a tanker is also provided.

Hydraulic apparatus with suitable electrical actuating means is disclosed for facilitating remote control of a number of operations including positive hold-down of one chamber mounted underwater atop another, sealing of one chamber to another, raising and lowering of the christmas tree within the capsule, and the coupling together of product-bearing lines in one chamber to product-bearing lines in an adjacent chamber.

18 Claims, 23 Drawing Figures PATENTEUMAY 9 I972 sum 010F 17 INVENTORS. JAMES VINCENT HARRINGTON, EDMUND QTRAGESER 8 JOHN E. BLANDING W, 11AM, W wRmr-w w 'heir ATTORNEYS PATENTEDHAY 9|972 9.661204 SHEET 03 [1F 17 INVENTORS ES VINCENT HARRINGTON EDMUND C. TRAGESER 8 JOHN E. BLANDING their ATTORNEYS.

PATENTEDMAY 91972 3,661,204

s um on HF 17 IN V EN TORSA JAMES VINCENT HARRINGTON, EDMUND C. TRAGESER 8:

JOHN E BLANDING W. haw, $01M! km 1 their ATTORNEYS.

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PATENTEDMAY 91972 3661204 sum 08 [1F 17 WE .TORS JOHN E. BLANDING,

EDMUND c. TRAGESER a JAMES VINCENT HARRINGTON W hw @amhm v R AJ iheir ATTORNEYS EATEHTEU MY 9 I972 sum 09 0F 17 FIG. /2

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lI-J WEI FFORS JOHN E. BLANDINQ EDMUND C. TRAGESER 8| JAMES VINCENT HARRINGTON their ATTORNEYS PATENTEDMAY 9 m2 SHEET 1SUF17 xn I 1 5903 90 5906 INVENTORS JOHN E. BLANDING EDMUND C.TRAGESER 8| JAMES VINCENT HARRINGTON their ATTORNEYS PATENTEB MY 9 I972 SHKEI 18 [1F 17 "E s i 606 INVENTORS JOHN E. BLANDING EDMUND C.TRAGESER a. 2/ JAMES VINCENT HARRINGTON W. 1 w, LQmMwRW ir ATTORNEYS PATENTEDMY 9:972 3,661,204

SHEET 17 0F 17 IN VI-IH'IT )RS JOHN E. BLANDING. EDMUND C. TRAGESER 8: JAMES VINCENT HARRINGTON ATTORNEYS CROSS REFERENCES TO RELATED APPLICATIONS This is a division of our application Ser. No. 671,532, filed Sept. 11, 1967, now U.S. Pat. No. 3,503,443, which is a division of our application Ser. No. 193,040, filed Apr. 26, 1962, now U.S. Pat. No. 3,353,364, which in turn is a continuationin-part of our application Ser. No. 81,543, filed .Ian. 9, 1961, now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to underwater drilling methods and apparatus and, more particularly, to novel methods and apparatus permitting a separation of the drilling, producing, and servicing phases of underwater well construction and operation.

The rapid depletion of the natural resources underlying the earths land masses and the growing demand for raw materials have led to an urgent quest to develop means for exploiting deposits beneath the floor of the sea and in other areas underlying water. A number of devices have been developed for this purpose, including notably the mobile platforms now in operation off the coasts of the United States mainland. However, conventional mobile platforms and similar apparatus have not provided a complete solution to the problem.

It is an object of the present invention, accordingly, to provide new and improved means for drilling, operating and servicing wells under the water.

A further object of the invention is to provide new and improved means for enclosing an underwater wellhead, keeping it dry, and enabling workmen to gain access to it for well maintenance.

Still another object of the invention is to provide means for lowering workmen to the wellhead for inspection and maintenance purposes.

Another object of the invention is to provide separate pieces of equipment to accomplish the drilling, operating, and servicing of underwater wells, including means for drilling a well, a watertight capsule for enclosing the wellhead, and personnel-carrying means for servicing the equipment at the wellhead at periodic intervals.

Another object of the invention is to make possible the replacement of conventional platforms by a small underwater capsule which is inexpensive and undisturbed by weather and shipping.

SUMMARY OF THE INVENTION These and other objects are attained, in a first representative embodiment of the invention, by providing a submersible vessel which is outfitted with the accouterments of the well driller. Attached to the vessel's exterior surface is a watertight capsule adapted sealably to pass drilling and easing means. Drilling means are extended from the vessel through the capsule for drilling a well, and casing is inserted into the well and sealed to the capsule. When the well is completed, the capsule and the vessel are sealed off from each other and separated. The capsule remains on the floor of the sea enclosing the wellhead and keeping the equipment at the wellhead dry, and the vessel is available for drilling another well. At periodic intervals a service chamber may be lowered to facilitate inspection and repair of the equipment at the wellhead. A line extending from the capsule to a float on the surface or a coded transponder on the capsule facilitates relocation of the capsule.

A second embodiment of the invention has numerous features which adapt it particularly for shallow-water drilling. For example, means are provided for mounting blowout preventors above the waters surface.

A third embodiment of the invention, adapted particularly for drilling in great water depths, has many novel features including novel hold-down equipment for holding down underwater-well apparatus. The apparatus so held includes a plurality of submersible chambers mounted upon a wellhead in vertically-stacked relation on a floor underlying water.

BRIEF DESCRIPTION OF THE DRAWING For an understanding of further particulars of the invention, reference may be made to the following detailed description of three representative embodiments thereof and to the accompanying figures of the drawings, in which: FIGS. 1-6 illustrate the first embodiment, FIGS. 7-13 the second, and FIGS. I l-22 the third. More particularly:

FIG. 1 is a perspective view, partially broken away, of a submersible vessel supported by a foundation pad on a floor underlying water and sealably attached to a watertight capsule in accordance with a first representative embodiment of the invention;

FIG. 2 is a detailed view in elevation (partly sectioned along the line 2--2 of FIG. 4) of the capsule as it appears when it is attached to the submersible vessel and has typical drilling equipment in place;

FIG. 3 is a detailed view in elevation (partly sectioned along the line 3-3 of FIG. 4) of the capsule as it appears after completion of the well, substitution of well-completion equipment for the drilling equipment, placement of a watertight hatch on the capsule, and departure of the submersible vessel;

FIG. 4 is a plan view, partially broken away, showing the construction of the capsule-hatch seal;

FIG. 5 is a diagrammatic representation of a service chamber being lowered from a tender to the capsule at the wellhead for the purpose of facilitating inspection or repairs in accordance with the invention;

FIG. 6 is a view in elevation, partially broken away, of the service chamber in position on top of the capsule and forming a watertight seal therewith;

FIG. 7 is a perspective view of apparatus for lowering a capsule support easing into a conductor pipe driven or otherwise placed into a shallow-sea floor in accordance with the invention:

FIG. 8 is a partly-sectioned elevational view of a drilling capsule particularly suited for drilling in relatively shallow water;

FIG. 9 is a partly-sectioned fragmentary elevational view of the mechanism by which the watertight integrity of the capsule shown in FIG. 8 is established along an annular junction of upper and lower halves of the capsule and by which the upper half is guided into sealing relation with the lower half;

FIG. 10 is a partly-sectioned detailed elevational view of one form of adaptor constructed in accordance with the invention;

FIG. 11 is a vertical sectional view of a wellhead and associated means constructed in accordance with the invention for hanging a plurality of casings down into a well during a drilling operation and for supporting a plurality of upper casing extensions associated therewith;

FIG. 12 is a partly-sectioned elevational view of a production capsule particularly adapted for use in relatively shallow waters;

FIG. 13 is a partly-sectioned fragmentary elevational view of a hydraulic lifting device shown also in FIG. 12;

FIG. 14 is a diagrammatic view of an overall arrangement of capsule, adaptor, separating equipment, production buoy, underwater storage tank, surface vessel and other apparatus particularly adapted for use in connection with wells drilled in great depths of water;

FIG. 15 is a partly-sectioned elevational view of a conductor pipe and a foundation pad which are being prepared at great depth to receive a drilling capsule;

FIG. 16 is a partly-broken away and partly-sectioned elevational view of a capsule enclosing a wellhead on the floor of the sea, the structure being particularly adapted for use in drilling in great depths of water;

FIG. 17 is a partly-sectioned elevational view of a deepwater capsule having well-completion valves in place and hydraulically-operated hold-downs from a superior chamber inserted in hold-down tubes attached to the capsule;

FIG. 18 is a partly-sectioned elevational view of a novel adaptor for use with the capsule shown in FIG. 17;

FIG. 19 is a partly-sectioned elevational view of separating apparatus mountable on the adaptor of FIG. 18;

FIG. 19A is a fragmentary sectional view taken along the line 19A--19A of FIG. 19 and looking in the direction of the arrows;

FIG. 20 is a diagram of novel electrohydraulic apparatus for operating hydraulic hold-down tubes, latching mechanisms and inflatable seals constructed in accordance with the invention;

FIG. 21 is a partly-sectioned elevational view of a centerline elevator or submersible personnel chamber constructed in accordance with the invention; and

FIG. 22 is a partly-sectioned elevational view of a production buoy constructed in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS While for purposes of exposition the three embodiments are treated separately, various apparatus and methods described in connection with one embodiment may also be used in combination with apparatus and methods which are described as relating to another embodiment.

FIRST EMBODIMENT: DRILLING A WELL FROM A SUBMERSIBLE VESSEL In FIG. 1 a submersible vessel is shown permanently secured to a foundation pad 11 at the bottom of the sea by remotely-controlled vertical adjustors 13. As many adjustors are used as may be necessary, and, in any event, other adjustors similar to the ones shown are located on the side of the vessel 10 opposite the side visible in the figure, so that the vessel 10 is provided with at least four legs" formed in a manner hereinafter set forth to hold down the vessel 10 and make final adjustments in its position when it arrives at the bottom.

The adjustors 13 are permanently attached to the vessel 10 and comprise cylinders 13a fitting sealably about rams 13b slidably mounted therein. Ram extensions 130 which extend downwardly from the rams 13b and sealably through the bottoms of the cylinders 13a to form the legs," are secured to the pad 11 by ball-in-socket connections Be or other (preferably universal) connections. Fluid lines 13d communicate with opposite ends of the cylinders 13a and extend to conventional apparatus (not shown) mounted within the vessel 10 for supplying a fluid to and exhausting it from the cylinders 13a, so that the ram extensions 13c may be remotely moved upwardly or downwardly to provide proper control of the position of the vessel 10.

A capsule 14 extending through a hole 15 in the pad 11 forms a watertight seal at its upper end with the vessel 10 by means of a mechanism indicated generally at 16, hereinafter described in detail, and at its lower end with a well casing 17.

Inasmuch as the pad 11 may settle during the drilling operation, it may be necessary to adjust the position of the vessel 10 with respect to the pad 11 by means of the adjustors 13 in order to preserve the seals at the end of the capsule 14. Relative vertical movement of the vessel 10 with respect to the pad 11 is readily effected by equal parallel movements of the adjustors 13. Limited horizontal movement of the vessel 10 with respect to the pad 11 is effected by certain unequal movements of the adjustors l3.

Lugs 18 help to establish the proper orientation of the capsule 14 with respect to the vessel 10 and thereby facilitate the forming of the seal by means of the mechanism 16. The lugs 18 are conveniently three in number and spaced at 120 intervals around the periphery of the capsule 14.

A traveling block 20 is used to lower a kelly 21, a drill pipe (not shown in FIG. 1), and the casing 17 into the capsule 14 and sealably through sealing means such as locks (not shown) in the bottom thereof.

FIG. 2 shows in detail the structure of the capsule 14 and the equipment associated therewith during the drilling process. The top 22 of the wellhead 23, which is securely mounted in and tightly sealed to the capsule 14, supports a double cellar gate 24 having a lower gate 25 and an upper gate 26. In accordance with the custom of the art, the cellar gate 25 is fitted with pipe rams (not shown), while the cellar gate 26 is fitted with blind rams (not shown). An annular preventer 27 is removably mounted on the double cellar gate 24, and an extension spool 28 extends upwardly from the top 29 of the preventer 27 for engagement with a drill-through blowout preventer 31.

The drill-through blowout preventer 31 comprises a lower stationary body portion 32 and an upper or "stripper portion 33, also stationary. While drilling is in progress, the kelly 21 is slidably and rotatably attached to the stripper portion 33 and extends downwardly through the portion 32 for engagement with a drill pipe 34 which drives a drill bit (not shown) at its lower end.

In accordance with standard drilling practice, all of the blowout preventers, including any additional preventers mounted between the extension spool 28 and the preventer 31, are remotely controlled, and drill bits and casing are passed or locked through the preventers and into the floor of the sea.

Mud return is provided for in the usual manner by an emergency high-pressure outlet 35 on the wellhead 23 which communicates through a valve 36 with a high-pressure mud-return line 37 and by a normal-pressure outlet 38 on the preventer 31 which communicates through a valve 39 with the high-pressure mud-return line 37 to form a combined-pressure mudretum line 40.

A closure plate 41, which is sealed to a flange 42 on the vessel 10 by means of bolts 43 and annular packing 44, prevents the entry of seawater into the interior of the vessel 10 in the event that the seal established by means of the mechanism 16 between the vessel 10 and the capsule 14 becomes ineffective during the drilling operation. A first opening 45 in the plate 41 is fitted with a removable gland 46, which forms a slidable seal about the spool 28. A second opening 47 in the plate 41 is fitted with a removable gland 48, which forms a seal about the high-pressure and mudaetum line 37. A manhole 49, the third and final opening in the plate 41, is provided with a cover 50, which is tightly sealable about its periphery to the plate 41.

The watertight seal between the vessel 10 and the capsule 14 is effected by a circular flange 42 on the vessel 10 and a mating flange 51 on the capsule 14 which are wedded by the mechanism 16 referred to above. The mechanism 16 includes a lever 52 for turning a shaft 53 at the end of which a pinion 54 engages a ring gear or annulus 55. The annulus 55 has a dovetail circular tongue 56 which fits within a dovetail circular groove 57 in the bottom of the vessel 10 so that the annulus can be freely rotated. When the annulus 55 is rotated, spacedapart inwardly projecting lips 58 on the annulus engage spaced-apart outwardly projecting lips 59 formed around the circumference of the flange 51. The lips 58 and 59 are inclined to form portions of helices, so that the vessel 10 and capsule 14 are drawn tightly together when the annulus 55 is rotated in one direction and are disengaged from each other when the annulus is rotated in the opposite direction. Suitably placed packing or gaskets at 60, 61 and 62 ensure a watertight seal. A collar 63 on the shaft 53 maintains the vertical position of the shaft regardless of the pressure of the sea.

Thus it will be seen that drilling can be conveniently accomplished from the submerged vessel 10 by personnel who are not subjected to the hazards of working while exposed to the great pressures which prevail in the ocean depths.

After the drilling of the well is completed the well-drilling equipment is removed from the capsule 14, well production equipment is put in place, a hatch 64 is put onto the capsule l4, and the vessel 10 withdraws; see FIG. 3. The cementing of the casing 17 may be accomplished in a conventional manner.

The well completion equipment illustrated in FIG. 3 includes a christmas tree 65 which has one or more master valves 66 and wing connections 67 and 68 which pass sealably through the capsule 14 for the delivery of oil. Wing valves 69 and 70, respectively, control the flow of oil through the wing 

1. Apparatus for drilling and servicing underwater wells comprising a hollow watertight submersible vessel, a hollow watertight capsule engageable with and disengageable from the vessel, drilling means extensible from said vessel through the capsule for drilling a well with the capsule enclosing the wellhead, a hollow watertight service chamber, means for moving the chamber between the surface of the water and the capsule, sealing means for forming a watertight seal between the chamber and the capsule, and means on the chamber and the capsule and within the sealing means for permitting access to the wellhead.
 2. Apparatus for drilling and servicing underwater wells comprising a hollow watertight submersible vessel, drilling means in said vessel for drilling an underwater well, a hollow watertight service chamber having a hatch surrounded by a first sealing means, a hollow watertight capsule enclosing the wellhead of said well and having a hatch surrounded by a second sealing means whose shape conforms to the shape of the first sealing means, means for lowering the chamber to the capsule, and means for landing the chamber on the capsule with the two sealing means in mating relation, whereby the wellhead remains dry and workmen have access thereto.
 3. The apparatus defined in claim 2, and further comprising packing between the two sealing means and projecting spaced-apart lips on the chamber engageable with oppositely-proJecting spaced-apart lips on the capsule for pressing the two sealing means together against the packing.
 4. Apparatus for drilling and servicing underwater wells comprising a hollow watertight submersible vessel, a hollow service chamber having a watertight compartment in its upper portion and a diving-bell configuration in its lower portion, a watertight hatch connecting the two portions and a first sealing flange at the bottom of the lower portion, a hollow watertight capsule engageable with a selected one of said vessel and said chamber and enclosing a wellhead, a hatch on the upper part of the capsule, a second sealing flange around the hatch conforming to the shape of the first sealing flange, means for lowering the chamber to the capsule, landing means for landing the chamber on the capsule with the sealing flanges in mating relation, packing between the flanges, means for pressing the flanges together against the packing, and a pump for removing water from the lower portion of the chamber, whereby the wellhead remains dry and workmen have access thereto from said vessel or said chamber.
 5. The apparatus defined in claim 4 in which the landing means are lugs projecting from the capsule and a line extending from the capsule and adapted to be taken up within the chamber.
 6. Apparatus for drilling and servicing underwater wells comprising a hollow watertight submersible vessel, a hollow watertight capsule attached thereto, drilling means extensible from said vessel through the capsule for drilling a well with the capsule enclosing the wellhead, completion means for completing the well after the drilling thereof, means for separating the capsule and the vessel, whereby the vessel can depart and the capsule remains enclosing the wellhead, a hollow watertight service chamber, means for moving the chamber between the surface of the water and the capsule, sealing means for forming a watertight seal between the chamber and the capsule and means on the chamber and the capsule and within the sealing means for permitting access to the wellhead.
 7. Underwater well-drilling and servicing apparatus comprising a hollow watertight submersible vessel, an evacuated capsule engageable with and disengageable from said capsule, an upper sealed hatch on the capsule, well casing sealably attachable to the capsule and projecting downwardly into the well, a line extending from the surface to the capsule, a service chamber adapted to service the capsule, a hatch in the chamber, means in the chamber to engage and draw the line into the chamber to propel it down to the capsule, and means to attach and seal the capsule to the chamber, whereby the well can be drilled from the submersible vessel and the chamber and capsule hatches may be opened when the chamber is sealed to the capsule to provide access to the capsule from the chamber.
 8. Underwater drilling apparatus comprising a hollow watertight submersible vessel, a capsule adapted to be lowered underwater by said vessel, a wellhead secured in and sealed to the capsule, blowout preventers disposed above the wellhead, drilling and casing means adapted sealably to be inserted through the blowout preventers and wellhead for drilling a well, and a service chamber adapted to be lowered and sealed to the capsule after completion of the well to provide access thereto.
 9. Underwater drilling apparatus comprising a submersible vessel, a watertight capsule adapted to form a seal with the vessel, a watertight plate on the vessel within the seal, a manhole in the plate providing access to the capsule, a cover for the manhole, a wellhead secured in and sealed to the capsule, a double cellar gate blowout preventer and an annular preventer adapted to be mounted in series above the wellhead, an extension spool adapted to be mounted above the double cellar gate and annular preventers and extending sealably through the plate, a drill-through blowout preventer adapted to be mounted above the extension spool, and drilling and casing means adapted Sealably to be inserted through the blowout preventers, extension spool and wellhead for drilling a well.
 10. The apparatus defined in claim 9 in which the drill-through blowout preventer comprises a stripper portion and a fixed portion and the drilling means includes a kelly attached to the stripper portion and extending through the drill-through blowout preventer, and further comprising a high-pressure mud-return line extending from the wellhead sealably through the plate and combining with a normal-pressure mud-return line extending from the drill-through blowout preventer to form a combined-pressure mud-return line.
 11. The apparatus defined in claim 10, and further comprising a hatch on the capsule, mating sealing flanges on the hatch and the capsule, and means for drawing the hatch and the capsule together.
 12. Apparatus for drilling and servicing underwater wells comprising a hollow watertight submersible vessel, a hollow watertight capsule attachable to and detachable therefrom, a wellhead secured in and sealed to the capsule, a master valve mounted on the wellhead, a wing connection extending from the master valve and passing sealably through the capsule, a wing valve on the wing connection, a transponder mounted on the capsule for identifying the capsule on demand, and a service chamber adapted to be lowered and sealed to the capsule to provide access thereto.
 13. Method of drilling and servicing underwater wells comprising the steps of drilling an underwater well from a submersible vessel, enclosing the wellhead with a hollow watertight capsule having a hatch thereon, lowering workmen in a hollow watertight service chamber having a hatch thereon to the capsule, forming a watertight seal between the chamber and the capsule around the hatches and opening the hatches, whereby the workmen have access to the wellhead.
 14. Method of drilling and servicing underwater wells comprising the steps of drilling an underwater well from a submersible vessel, enclosing the wellhead with a hollow watertight capsule having means adapted to land a service chamber and a hatch surrounded by a first sealing flange, lowering workmen in a service chamber having a hatch surrounded by a second sealing flange conforming to the shape of the first sealing flange to the capsule and landing the chamber on the capsule with the sealing flanges in engagement, drawing the sealing flanges together so as to effect a watertight seal between the chamber and the capsule, and opening the hatches, whereby the workmen have access to the wellhead.
 15. Method of drilling and servicing underwater wells comprising the steps of drilling an underwater well from a submersible vessel, enclosing the wellhead with a hollow watertight capsule having means adapted to land a service chamber and an upper hatch surrounded by a first sealing flange, lowering workmen to the capsule in a service chamber having a watertight compartment in its upper portion, a diving-bell configuration in its lower portion, and a hatch connecting the two portions surrounded by a second sealing flange, landing the chamber on the capsule with the sealing flanges in engagement, drawing the sealing flanges tightly together against packing to effect a watertight seal between the chamber and the capsule, pumping out water from the lower portion of the chamber, and opening the hatches, whereby the workmen have access to the wellhead.
 16. Method of drilling and servicing underwater wells comprising the steps of attaching a hollow watertight capsule to a hollow watertight submersible vessel, the capsule and vessel having communicating openings adapted to receive drilling means, extending drilling means from the vessel through the openings and capsule and sealably out the other side of the capsule and drilling a well with the capsule enclosing the wellhead, completing the well following the drilling thereof, effecting watertight closure of the openings, separating the vessel and the capsule, whereby the vessel can depart and the caPsule remains enclosing the wellhead, periodically lowering workmen to the capsule in a hollow watertight service chamber having a hatch, forming a watertight seal between the chamber and the capsule around the hatch and the opening on the capsule, and opening the hatch and the opening, whereby the workmen have access to the wellhead.
 17. Method of drilling and servicing underwater wells comprising the steps of drilling an underwater well from a submersible vessel, enclosing the wellhead with a watertight capsule sealably engaging the well casing and having a hatch, extending a line from the capsule to the surface, housing workmen in a hollow watertight service chamber having a hatch, drawing the line into the chamber, whereby the chamber is guided down to the capsule, forming a watertight seal between the chamber and the capsule around the hatches, and opening the hatches, whereby the workmen have access to the wellhead.
 18. Method of constructing, operating, and servicing underwater wells, comprising the steps of outfitting a submarine with well-drilling and completion equipment, releasably attaching to the exterior of the submarine a watertight capsule adapted sealably to pass drilling said casing means, submerging said submarine, extending drilling means from the submerged submarine through the capsule and drilling an underwater well, removing the drilling means from the well and capsule and inserting casing into the well and sealing the casing to the capsule, sealing off said submarine and said capsule from each other and separating said submarine from said capsule, whereby the submarine is available for drilling another well and the capsule remains enclosing the wellhead, and periodically lowering to said capsule a watertight service chamber adapted to form a watertight seal with the capsule, whereby inspection and repair of said capsule and the wellhead is facilitated. 